1. Field of the Invention
The present invention relates to a doping mask and methods of manufacturing a charge transfer image device and a microelectronic device using the same.
2. Description of the Related Art
A charge transfer image device is a device that transfers a photoexcited signal charge, which is generated by incident light and stored in a light-receiving region, to an output region to generate a voltage, thereby outputting image information. The charge transfer image device is a charge-coupled device (CCD) which is an image sensor. According to a signal transfer principle of the charge transfer image device, all pixel signals are at a time transferred to a device except pixels in an analog manner and then are sequentially read out.
The CCD is classified into a frame transfer type and an interline transfer type according to the transfer principle used by the device.
The CCD has a uniformly arrayed structure of a plurality of metal oxide semiconductor (MOS) diodes or P/N junction photodiodes. A frame transfer type CCD includes a camera unit converting incident light to a signal charge, a storage unit storing the signal charge, a horizontal transfer unit transferring the signal charge horizontally, and an output amplifier.
An interline transfer type CCD includes a photodiode generating a signal charge according to the intensity of incident light, a vertical transfer channel transferring the signal charge in a vertical direction, a horizontal transfer channel transferring the signal charge received from the vertical transfer channel in a horizontal direction, and an output circuit unit detecting the signal charge received from the horizontal transfer channel.
The charge transfer image device includes a pixel region including a photodiode, a vertical transfer channel, and a horizontal transfer channel, and a peripheral circuit region including an input/output circuit unit and an amplification circuit unit.
Here, the pixel region and the peripheral circuit region surrounding the pixel region are formed on a single sub-substrate.
In detail, since an operation voltage is constantly applied to a N-type sub-substrate on which all chips are mounted, in forming P-wells in the N-type sub-substrate, a P-well of the peripheral circuit region must be formed at a higher concentration than that of the pixel region in order to be connected to ground.
In this respect, conventional P-type ion implantation is performed in a two-step process using two masks, one of which is formed on the entire surface of the N-type sub-substrate for a first step and the other is formed on a surface of the N-type sub-substrate intended for the peripheral circuit region for a second step.
However, such a two-step doping process using two masks is can have drawbacks and is not cost-effective.